Insulating spacer

ABSTRACT

An insulating spacer comprising a central conductor, a cylindrically shaped metallic shield which is arranged around said central conductor and is partially in contact with said central conductor, an insulating member made of a thermosetting resin said shield is embedded into the inner diameter thereof and said central conductor is enclosed thereby, and a shield of the earth side which is deeply embedded into a outwardly extending flange portion of said insulating member, and also preferably comprises fiber-reinforced resin formed of fibrous tissues which is tightly wound around a plurality of independent grooves provided on the periphery of said central conductor and a thermosetting resin which is infiltrated into said fibrous tissues so that said insulating member formed of a thermosetting resin may be firmly fixed around over said central conductor, thus said insulating spacer being adapted to be applied to a duct line air power transmission bus bar, gas-filled breaker or the like in which a sulfur hexafluoride gas is employed as an insulating medium.

United States Patent I 1 1151 3,652,778

Sakai 1451 Mar. 28, 1972 [s41 INSULATING SPACER 1,133,270 11/1968 GreatBritain ..'.l74/28 [72] Inventor: Yoshikazu Sakai, Kagamihara, JapanPrimary Examiner Lammie E Askin [73] Assignee: NGK Insulators, Ltd.,Mizuho-ku, Kagoya, 'E mi" A-T- Grimley Japan Attorney-Craig, Antonelliand Hill 22 sneer Oct. 6, 1970 [57] ABSTRACT PP 78373 An insulatingspacer comprisinga central conductor, a cylindrically shaped metallicshield which is arranged around said [30] Foreign Applicatlon PriorityData central conductor and is partially in contact with said central Iconductor, an insulating member made of a thermosetting Oct. 16, 1969Japan ..44/98379 resin Said shield is embedded into the inner diameterthereof and said central conductor is enclosed thereby, and a shield of[52] US. Cl. ..174/28, 174/16 B, 174/36, the earth side which is deeplyembedded into a outwardly 174/99 B tending flange portion of saidinsulating member, and also [51] Int, Cl. ..H0lb 9/04 preferablycomprises fib i f d resin f d f fib [58] Field olSearch ..174/28,29, 165,99 8,21,

tissues which is tightly wound around a plurality of indepen- 174/36dent grooves provided on the periphery of said central conductor and athermosetting resin which is infiltrated into said [56] References Citedfibrous tissues so that said insulating member formed of a thermosettingresin may be firmly fixed around over said central UNITED STATES PATENTSconductor, thus said insulating spacer being adapted to be ap- ..174/28plied to a duct line air power transmission bus bar, gas-filled3,356,785 12/1967 Yoshida et al.. ..174/28 breaker or the like in whicha sulfur hexafluoride gas is em- 3,324,272 6/1967 Shankle et al......174/28 X ployed as'an insulating medium. 3,155,787 11/1964 Imhof..174/21 UX FOREIGN PATENTS OR APPLICATIONS 476,379 9/1969 Switzerland..174/23 3,391,243 7/1968 Whitehead 3 Claims, 5 Drawing FiguresINSULATING SPACER BACKGROUND OF THE INVENTION The present inventionrelates to an insulating spacer, and more particularly to an insulatingspacer which is to be employed for a duct line air power transmissionbus bar, a gasfilled breaker or the like in which a sulfur hexafluoridegas is mainly used as an insulating medium.

A type of insulating spacer having an insulating member formed of athermosetting resin such as epoxy resin in the prior arts has beencustomarily constructed in the manner that metallic flanges are fixed tothe periphery of the insulating member for said insulating member to besecured to an external duct and a central contuctor is fixedly connectedto the center of the insulating member for said central conductor topenetrate through the insulating member.

However, the construction as described above tends to cause gap spacesat the boundary portions between themetallic flange and the insulatingmember and as well between the central conductor and the insulatingmember in manufacturing steps, and moreover in operation of theinsulating spacer said gap spaces being caused and spread by respectivedifferences of the thermal expansion coeficients thereof while theexpansion and contraction due to the variable heat exerted. Accordingly,it is impossible to obtain any satisfactory gas-tightness and as well toprevent corona discharge from being generated even under low voltage.

Although a method in which a semiconductive adhesive is employed inorder to solve the problems as above described has been attempted to bepracticed, it has been impossible to obtain a satisfactory effect bythis method.

The present invention has been completely accomplished with an object ofeliminating the above mentioned disadvantages and then an insulatingspacer according to this invention comprises a central conductor, acylindrically shaped metallic shield arranged around said centralconductor and partially in contact with said central conductor, aninsulating member consisting of a thermosetting resin with saidcylindrically shaped metallic shield being embedded into the inner wallthereof as to enclose said central conductor therewithin,

I and a shield of the earth side which is deeply embedded into a flangeportion of said insulating member, and also preferably comprisesfiber-reinforced resin formed of fibrous tissues which is tightly woundarround a plurality of. independent grooves provided on the periphery ofsaid central conductor and a thermosetting resin which is infiltratedinto said fibrous tissues so that said insulating member formed of athermosetting resin may be firmly fixed around over said centralconductor, thus said insulating spacer being adapted to be applied to aduct line air powertransmission bus bar, gas-filled breaker or the likein which a sulfur hexafluoride gas is employed as an insulating medium.

SUMMARY OF THE INVENTION According to the present invention, there isobtained a much more improved insulating spacer as compared with that ofthe prior art, and the insulating spacer of the present inventioncomprises a central conductor and an insulating member provided aroundsaid central conductor, and as Well is characterized in that acylindrically shaped metallic shield being arranged on the periphery ofsaid central conductor and made partially in contact with said centralconductor, said central conductor being enclosed by the insulatingmember formed of a thermosetting resin for said cylindrically shapedshield to be embedded into said insulating member, and a shield portionof an earth side shield being deeply embedded into an outwardlyextending flange portion of said insulating member, and furtherpreferably characterized in that said central conductor being providedwith a plurality of annular grooves on the periphery thereof, and eachof said grooves being filled with reinforced plastic layer formed offibrous tissues which is tightly wound with tension around each of saidgrooves and a thermosetting resin which is infiltrated into said fibroustissues.

The primary object of the present invention is to provide a much morehighly efficient insulating spacer means which is adapted to be appliedto a duct line air power transmission bus bar, gas-filled breaker or thelike for extremely high voltage.

Another object of the present invention is to provide an insulatingspacer improved in that the insulating member formed of a thermosettingresin is firmly fixed around over the central conductor for eliminatinggap spaces which tends to cause undesirable condition, that is coronadischarge or deterioration of insulation.

The other advantages or characteristic features of the present inventionwill be described in detail in the following descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERREDEMBODIMENTS Referring now to FIG. 1, the reference numeral 1 designatesa tubular or rod like central conductor, and the central conductor isarranged to be embedded as to penetrate through the center of aninsulating member 2 formed of a thermosetting resin such as epoxy resinor the like and is also provided with annular projections 3,3 at theembedded portion therearound in'a suitably spaced relation. A cylinder 4made of a conductive material such as a metallic foil, a metal plate orametallic meshes is closely arranged around the central conductor 1between the annular projections 3,3 and is connected to the centralconductor, thereby a shield 4 of the conductor side is provided as to beembedded into the inner wall of said insulating member 2. g

The reference numeral 5 designates a shield of the earth side, which isembedded coaxially with the central conductor 1 into a flange portion 2of the insulating member 2, and this earth side shield 5 consists of anannular shield portion 6 made of a conductive material such as ametallic foil, a metal plate or a metallic meshes as similar to that ofthe shield 4' and formed into the shape of a channel in cross section asshown in FIG. 1b, a plurality of conductive portions 7 provided on theannular shield portion 6, and cylindrical brackets 8 provided at therespective ends of the conductive portions 7. Each of the brackets 8 ismade to penetrate through the flange portion 2' of the insulating member2 so that adjacent external ducts 10 may be fixedly joined at theprojected flanges 10 thereof together with the insulating member 2 bymeans of bolts 9 inserted through the brackets 8.

In addition, the central conductor 1 is provided with a plurality ofindependent annular grooves 11 having the dimensions, for an example, ofapproximately 10 mm. in width, approximately 3 mm. in depth andapproximately 10 mm. in pitch, and each of the grooves is filled withreinforced plastic layer 12 that is so called FRP formed of fibroustissues such as roving, cloth or tape which is tightly wound withtension around said annular grooves 11 and a thermosetting resin such asepoxy resin or the like which is infiltrated into said fibrous tissues.

When the insulating member 2 formed of a thermosetting resin materialsuch as epoxy resin or the like as above mentioned is put over aroundthe central conductor after each of the annular grooves 11 have beenpreviously filled with the reinforced plastic layer 12, since thereinforced plastic layer 12 is also formed of substantially the samethermosetting resin as the insulating member 2, the insulating membermay be I V positively integrated together with the reinforced plasticlayer.

Furthermore, since the thermal expansion coefficient of the reinforcedplastic layer 12 is provided with an intermediate value between that ofthe central conductor 1 made of a metal and that of the insulatingmember 2 made of a thermosetting resin, the reinforced plastic layer 12serves as a buffer layer against the thermal shock caused between thecentral conductor l and the insulating member 2.

Additionally, any occurrence of corona discharge due to foams involvedin the reinforced plastic layer 12 may be prevented by means of themetallic shield 4, and in case of this shield being formed of a metallicmeshes the insulating member 2 formed of a thermosetting resin can berigidly fixed to the reinforced plastic layer 12 by impregnating saidmeshes with said resin without gap spaces.

Still further, since each of the annular grooves l l filled with thereinforced plastic layer 12 is independently arranged, assuming thatpartial break away would be caused between the central conductor 1 andthe reinforced plastic layer 12, this break away is effectivelyprevented from further spreading into the other portion of the layer.

FIG. 2 shows an another embodiment of the present invention which isdifferent from FIG. 1a only in that annular projections as indicated 3,3in FIG. la are omitted and an insulating member 2 is formed upright.

FIG. 3 shows an insulating spacer of the prior art in which gap spacestends to be brought about at the adhesive boundary area 14 between theinsulating member '2 and the metallic flange portion 13 arranged on theperiphery of the insulating member 2 and at the boundary area 15 betweenthe central conductor 1 and the insulating member 2.

In case that the insulating spacer which is constituted as abovementioned according to this invention is practiced with sulfurhexafluoride gas being charged into each of closed chambers defined bythe central conductors 1, external ducts 10 and the insulating spacers,since the shield portion 6 of the earth side shield 5 is deeply embeddedinto the flange portion 2' of the insulating member 2 formed ofthermosetting resin such as epoxy resin or the like, any gap space isnot brought about at the area of the earth side shield 5, and since theconductor side shield 4 is also firmly embedded into the insulatingmember 2 in connection with the central conductor 1, any gap space isnot brought about as well at the area of the conductor side shield 4.Accordingly, it can be effectively prevented from occurring that theinsulating material is eroded by a resolved gases of the sulfurhexafluoride gas caused by the corona discharge, thus resulting in theinsulation deterioration and damage of the insulating spacer beingeliminated.

The results in a comparison test with respect to the flashovercharacteristics by changing the pressure of the sulfur hexafluoride gasfilled in each of the closed chamber provided between the adjacentinsulating spacers which have the dimensions of mm. in the outerdiameter of the central conductors l and of 600 mm. in the innerdiameter of the external ducts 10 are as shown in a graph of FIG. 4, andthe insulating spacer according to the present invention proves to bemuch more improved in that any insulation deterioration does not appeareven at the high pressure region of the sulfur hexafluoride gas ascompared with that of the prior art.

lclaim:

1. An insulating spacer comprising a central conductor and an insulatingmember provided around said central conductor, characterized in thatsaid central conductor is provided with a plurality of grooves on theperiphery thereof, each of said grooves is filled with reinforcedplastic layer formed of fibrous tissues which is tightly wound withtension around each of said grooves and a thermosetting resin which isinfiltrated into said fibrous tissues, a cylindrically shaped metallicshield is arranged on the periphery of said central conductor and madepartially in contact with said central conductor, said central conductoris enclosed by the insulating member formed of a thermosetting resin forsaid cylindrically shaped shield to be embedded into said insulatingmember, and a shield portion of an earth side shield is deeply embeddedinto an outwardly extending flange portion of said insulating member.

2. An insulating spacer as defined in claim 1 wherein the thermosettingresin infiltrated into the reinforced plastic layers and thethermosetting resin formed into the insulating member are epoxy resin.

3. An insulating spacer as defined in claim 1 wherein the shield portionof the cylindrically shaped metallic shield and the earth side shieldare formed of a metallic meshes.

1. An insulating spacer comprising a central conductor and an insulatingmember provided around said central conductor, characterized in thatsaid central conductor is provided with a plurality of grooves on theperiphery thereof, each of said grooves is filled with reinforcedplastic layer formed of fibrous tissues which is tightly wound withtension around each of said grooves and a thermosetting resin which isinfiltrated into said fibrous tissues, a cylindrically shaped metallicshield is arranged on the periphery of said central conductor and madepartially in contact with said central conductor, said central conductoris enclosed by the insulating member formed of a thermosetting resin forsaid cylindrically shaped shield to be embedded into said insulatingmember, and a shield portion of an earth side shield is deeply embeddedinto an outwardly extending flange portion of said insulating member. 2.An insulating spacer as defined in claim 1 wherein the thermosettingresin infiltrated into the reinforced plastic layers and thethermosetting resin formed into the insulating member are epoxy resin.3. An insulating spacer as defined in claim 1 wherein the shield portionof the cylindrically shaped metallic shield and the earth side shieldare formed of a metallic meshes.